The invention relates to a device for changing a blade on shears, in particular for a rolled band and to such shears.
In the case of shears for cutting or cross cutting a rolled band, the blades attached to the shears generally have to be changed because the blades are subject to severe wear during operation of the shears. Accordingly, the fastenings with which the blades are attached to the shears can be released in order to suitably exchange the blades.
In the prior art, blade fastenings in the form of screws of screw bolts, which can be simply released for replacing the blades, are known for shears of this type. However, such fastening means are subject to the following disadvantages: because of the action of heat and media during operation of the shears, the screws or screw bolts can have a tendency to stick after quite some operating time, and therefore the changing of the blades is time-consuming. After tightening of the fastening screws, a blade settles after a number of cuts by the shears, and therefore the screws lose the necessary tensioning for clamping the blade. Finally, a further disadvantage of such blade fastenings consists in that the screws or screw bolts are generally handled manually, which leads to long reequipping times with correspondingly high costs.
In order to avoid the above disadvantages, solutions are conventionally known in which the blades are fastened to a blade carrier of the shears with spring elements, preferably in the form of disk springs, wherein pretensioning of the spring elements brings about automatic clamping of the blades on the blade carrier. The tensioning for clamping the blades always stays constant here, with it simultaneously also being possible to avoid sticking of screw elements or the like.
The blades can be released from the blade carrier of the shears hydraulically using hydraulic cylinders, as a result of which changing of the blades is advantageously possible in a short time.
According to the prior art, for example in DE 34 23 275 A1, DE 30 30 744 A1 or CN 202 57 14 56 U, the use of hydraulic cylinders in drum shears is known, wherein the hydraulic cylinders are arranged within a blade drum of the drum shears. A disadvantage in this connection is that the release force of the hydraulic cylinders installed in the blade drum is restricted because of the small structural dimensions, as are the clamping forces of the spring elements, for the same reason. Furthermore, the seals of the hydraulic cylinders are heat-sensitive, and therefore the blades and the blade drums have to be cooled in a complicated manner in order to restrict component temperatures. Further disadvantages consist in that the necessary bores for supplying hydraulic oil to the hydraulic cylinders within the blade drum have to be produced in a complicated manner, and that the connections for the hydraulic oil to the hydraulic cylinders have to be made in a complicated manner on the outer side of the shears.